An absolute grating scale is mainly used as a full-closed loop in a high-end numerical control system, and has advantages that absolute positions can be obtained as long as the system is powered on, a zero position does not need to be searched, and moreover, optical detection is adopted, and the absolute grating scale is not wearable due to adoption of a non-contact structure. The absolute grating scale is a necessary key part in the numerical control industry in the future.
According to the absolute grating scale, absolute position codes are engraved on a glass scale board, and are projected onto a photodiode array by irradiation of parallel light, the photodiode array converts optical signals with absolute position information into electric signals, and the absolute positions can be known through analysis. However, due to some adverse factors such as nonuniform illumination intensity, low absolute code engraving quality, nonuniform photoelectric response of the photodiode array and the like, the finally output electric signals with the absolute positions are inconsistent, accurate judgment on the absolute positions is influenced, and accuracy of the absolute grating scale is reduced.
Therefore, in the production and manufacturing process of the absolute grating scale, a consistency correction method is required to make up the detects such that the absolute signals finally output by the absolute grating scale can accurately and precisely reflect the real absolute positions.
A method for consistency correction method of a photoelectric converter and its processing circuit is disclosed, as in the Chinese Patent Publication No. CN102300057A, which has a title of “Method for correcting response inconsistency of linear array CCD (Charge Coupled Device) image elements”. The patent discloses that response inconsistency of CCD image elements is corrected by a formula of Si=ki(yi−(bi*DC+ci*g)), and then digital gain adjustment is carried out on the correction result by a formula of pi=k*si, where pi represents a result after the digital gain adjustment, and k represents a gain factor. This method only corrects response inconsistency of CCD image elements in a manner of changing the gain factor and thus has problems that the liner range of the photoelectric response is narrow and signal dispersion is large.